This invention relates generally to laboratory slides on the type used for the examination and/or selected testing and analysis of liquid specimens, such as biological specimens and the like. More particularly, this invention relates to improved yet relatively simple and economical constructions for a laboratory slide having an examination chamber or flow channel of substantially monocellular height dimension, if desired.
Laboratory slides are used widely in the examination of a wide variety of liquid and liquid-based specimens. For example, laboratory slides are well known in the medical arts for supporting a specimen of biological origin, such as blood, serum, urine, and the like, to facilitate optical examination of the specimen for medical purposes, In the past, such laboratory slides have comprised a lower transparent slide plate upon which the specimen is placed and then covered by an overlying transparent coverplate, commonly referred to as a "coverslip." The coverslip spreads the specimen into a relatively thin film confined between the slide plate and coverslip to facilitate specimen handling in the course of specimen examination, for example, by microscope inspection to obtain a particle count or other visually perceivable information. One major disadvantage with laboratory slides of this general type, however, relates to the inability to repeatedly control the thickness of the specimen film between the slide plate and coverslip, wherein precise knowledge of the depth of the film is important to insure accurate test results, Variations in the film dimension undesirably lead to significant errors upon optical inspection.
In efforts to obtain a controlled and repeatable specimen film thickness, laboratory slides have been developed with the slide plate and coverslip molded integrally or otherwise rigidly affixed to each other and shaped to define a laterally open examination chamber into which a liquid specimen may be drawn by capillary action. See, for example, U.S. Pat. No. 3,777,283. While such slides advantageously insure consistency of specimen film thickness during examination, manufacturing size and tolerance limitations have prevented the use of extremely thin film thicknesses approaching substantially monocellular dimensions. Instead, available laboratory slides have been restricted to specimen film thicknesses corresponding with several cellular layers, such as 0.004 inch or larger, thereby requiring the laboratory technician to exercise considerable skill to examine the depth of field of the liquid specimen if accurate analysis is to be obtained. As a result, even with examination chambers of controlled height dimension as small as 0.004 inch, a significant margin of error remains.
There exists, therefore, a significant need for an improved laboratory slide having an extremely thin and closely controlled and preferably substantially monocellular spacing between a lower slide plate and an overlying coverslip. The present invention fulfills such needs and provides further related advantages.